Flash lamp and ignition means therefor



y 1962 R. M. ANDERSON ET AL 3,046,769

FLASH LAMP AND IGNITION MEANS THEREFOR Filed April 29, 1960 /0 T/ME-M/LL/5ECONDS 3 g A F m m mzm Sw IQ Invervtovs: Rober i: M. AndersonLouis A. Demchockflv. b3 eiT- jtorneg United States Patent M 3,046,769FLASH LAMP AND IGNITIGN MEANS TIEREFQR 1 Robert M. Anderson, Euclid, andLouis A. Demchock,

Cleveland, Ohio, assignors to General Electric Company, a corporation ofNew York Filed Apr. 29, 1960, Ser. No. 25,626 3 Claims. (Cl. 67-31) Ourinvention relates in general to flash lamps of the type used forphotographic purposes and comprising a sealed radiation-transmittingbulb in which is enclosed a readily combustible metallic material,together with suitable ignition means therefor, including a p'nmer orfulminating substance, and a combustion-supporting gas filling which,upon ignition of the lamp, enters into a reaction with the combustiblematerial with the resulting emission of a momentary flash of actiniclight of high intensity. More particularly, our invention relates to anignition means for such type flash lamps, and in particular to thecomposition of the fulminating or primer material thereof. The inventionis especially applicable to flash lamps of the type employing, as thecombustible light-producing material thereof, metallic filamentarymaterial in the form of wire or ribbon such as the so-oal-led shreddedfoil and consisting essentially of zirconium or of any other metallicmaterial having a' relatively low heat-energy ignition characteristicsubstantially corresponding to that of zirconium.

Because of the relatively low heat-energy ignition characteristic ofzirconium and its resultant exceedingly fast ignition, the peakintensity of the light flash produced by a flash lamp provided withfilamentary combustible material composed essentially of zirconium or amaterial having a similarly fast ignition characteristic substantiallycorresponding to that of zirconium, occurs within a considerably shorterintervalof time, following the closure of the electrical circuit to theignition filament of the lamp, than it does with a flash lamp ofsubstantially the same construction but provided instead withfilamentary combustible material composed of aluminum oraluminum-magnesium alloy such as has been generally employed heretofore.This shorter time to peak intensity characteristic of suchzirconium-type combustible material flash lamps is particularlypronounced in the case of extremely small size flash lamps of the typeprovided with a bulb of less than 2 cc. internal volume, for example.Thus, whereas a flash lamp of such small size and pro vided withfilamentary combustible material consisting essentially of aluminum maypossess a time to peak intensity of around 15 milliseconds following theclosure of the electrical circuit to the ignition filament of the lamp,the time to peak of a flash lamp of substantially the same construction,except provided instead with filamentary combustible material consistingessentially of zirconium, will occur at anywhere from to 13 millisecondsfollowing the closure'of the electrical circuit to the ignition filamentof the lamp.

While a flash lamp with such a comparatively short time to peakintensity nevertheless may still be used with some degree ofeffectiveness for so-called class F synchronization wherein a camerashutter is opened to its fully open position, by means of a synchronizerdevice, at approximately 15 milliseconds following the start of theshutter actuating operation, the considerably shorter time to peakintensity characteristic of such small size zirconium filled flash lampsrenders them entirely unsuitable for so-called class M synchronizationwherein the camera shutter opens to its fully opened position atapproximately 2.0 milliseconds following the start of the shutteractuating operation. This is because of the fact that by the time theshutter has reached its fully open position at the 20 millisecond timeinterval, the light intensity of the light flash from the zirconiumfilled lamp has fallen off to such a low level as to be of practicallylittle eflective value for picture-taking purposes. To be effectivelyutilizable, therefore, for class M synchronization as well as for classF synchronization, such an extremely smally size zirconiumfilled flashlamp should have its light flash reach its peak intensity at around 15to 16 milliseconds following the closure of the electrical circuit tothe ignition filament of the lamp, and such a peak time should beobtained without any adverse effects on the performance and operabilitycharacteristics of the lamp such as its total light output and peakintensity, or the electrical power required to flash the lamp (i.e., thelamp flashability) and the freedom of the lamp from filament burn-outwithout the lamp flashing. :In this way, it is assured that asufficiently high level of light will still be present, at the 20millisecond time interval following closure of the electrical circuit tothe lamp filament, to be effective for picture-taking purposes withclass M synchronization.

While the desired longer time to peak intensity of the light flashproduced by such small size zirconium-filled lamps could be easilyaccomplished by simply reducing the physical size or quantity of theprimer coatings or beads on the lead-in wires of the lamp, such anexpedient would be impractical from a manufacturing standpoint becauseof the difliculty of maintaining the degree of control over such smallersize primer coatings on the lead-in wires which would be necessary inorder to keep them within the size variation limits required to maintainuniformity in the light performance characteristics of the lamps such astotal light, peak light and time to peak. With such smaller size orquantities of the primer coatings on the lead-in wires, the slightvariations which are normally encountered in the size or quantity of thefinal primer coatings, with practical manufacturing procedures such asconventionally employed at present, would in such case be so great as tocause unacceptable variations in the light performance characteristicsof the lamps. Accordingly, any solution to the aboveanentioned problemof short peak time should not involve the reduction in the size orquantity of the primer coatings or beads on the lead-in wires beyond theminimum workable size for effective manufacturing cont-1'01 thereover.

In addition to the undesirably shorter peak time of such extremely smallsize zirconium-filled flash lamps as constructed heretofore, such lampsare further characterized by their high susceptibility to accidentalflash-outs by electrostatic charges. For example, flash lamps of suchconstruction are apt to be flashed by the electrostatic charge which isproduced on the bulb surface when the lamp is merely brushed against theclothing of one handling the lamp, as when being placed in aphotographers coat pocket, for instance. In fact, entire packing sleevesand hampers of such lamps have been accidentally set off byelectrostatic charges. As a consequence, it has been necessaryheretofore, in the manufacture of such extremely small sizezirconium-filled flash lamps, to exercise the utmost safety precautions,including the wearing by manufacturing personnel of special apparel notconducive to the production of electrostatic charges, in order toprevent the occurrence of any such accidental flashouts of the lamps byelectrostatic charges with resulting likelihood of sustaining burns orother bodily injury.

It is an object of our invention, therefore, to provide an extremelysmall size flash lamp of the type provided with filamentary combustiblematerial consisting essentially of zirconium, or of a material having arelatively low heat-energy ignition characteristic substantiallycorresponding to that of zirconium, and having an appreciably longerpeak time for the light flash produced by the lamp, as compared to priorflash lamps of such type, while capable of producing at least as muchtotal light and peak light intensity.

Another object of our invention is to provide an extremely small sizeflash lamp of the type provided with filamentary combustible materialconsisting essentially of zirconium and having a peak time of around 15to 16 milliseconds, while producing at least as much total light andpeak light intensity as prior flash lamps of such type, whereby the lampis satisfactorily utilizable for both class F and class Msynchronization.

Still another object of our invention is to provide an extremely smallsize flash lamp of the type provided with filamentary combustiblematerial consisting essentially of zirconium and of markedly reducedsusceptibility to accidental flash-out, by the electrostatic charges towhich the lamp is normally subjected during manufacture and use, ascompared to prior flash lamps of such type.

A further object of our invention is to provide an improved primercomposition for the ig'nition means of a flash lamp of the typeemploying filamentary combustible material composed essentially ofzirconium, or of a material having a relatively low heat-energy ignitioncharacteristic substantially corresponding to that of zirconium, whichprimer composition is eflective to not only markedly reduce thesusceptibility of such lamps to accidental flash-out by electrostaticcharges applied thereto, but to also retard the peak time of the lightflash produced by the lamp without any attendant loss in either itstotal light output or its peak light intensity.

Briefly stated, in accordance with one aspect of ur invention, the lampignition primer or fulminating material in flash lamps of the typeemploying filamentary combustible material consisting essentially ofzirconium, or of a material having a relatively low heat-energy ignitioncharacteristic substantially corresponding to that of zirconium, ismodified by the incorporation in the primer material of a definiteamount of one or more inert additive materials effective to markedlyretard the peak time of the light flash produced by such a lamp Withoutany attendant loss in the total light or in the peak light intensityproduced by the lamp.

Further objects and advantages of our invention will appear from thefollowing detailed description of species thereof and from theaccompanying drawing.

In the drawing, FIG. 1 is an elevation, partly in section, of a flashlamp comprising our invention.

FIG. 2 is an enlarged view of the ignition means comprising ourinvention, and

FIG. 3 is a chart showing the time-light characteristic curve of a flashlamp comprising our invention as compared to that of prior flash lampsof comparable size and character.

Referring to FIG. 1, the invention is there shown as embodied in aminiature type flash lamp such as disclosed and claimed in copendingapplication Serial No. 808,981, R. M. Anderson, filed April 27, 1959 andassigned to the assignee of the present invention, and comprising a verysmall size sealed glass envelope or bulb 1 approximately of tubularshape and consisting of a short length of drawn glass tubing closed atone end by an integral fiattened external stem press 2 protrudingaxially from the bulb, and necked down and closed at its other end by anend wall portion 3 terminating in an exhaust tip 4. The particular bulb1 illustrated has an internal volume f less than 2 cc. and preferably ofthe order of 1.2 cc., andthe tubular portion of the bulb (i.e., the bulbproper) has an outside diameter of the order of A inch and a length ofthe order of inch. The opposite sides 5 of the stem press 2 are formedas flat surfaces preferably disposed approximately parallel to eachother and to the axis of the bulb. As shown, the said flat sides 5 ofthe stem press 2 are provided with transversely extending guidechannelways or grooves 6 for sliding engagement with cooperating guidetrack means of a lampholding magazine or feeding chamber (not shown) ofa lamp flashing apparatus.

The bulb 1 contains a loosely distributed filling of a readilycombustible metallic material 7 in filamentary form and consisting ofzirconium or an alloy essentially composed of zirconium, or of anymaterial having a relatively low heat-energy ignition characteristicsubstantially corresponding to that of zirconium. The filamentarycombustible material 7 preferably is in the form of fine cut strands ofa thin foil of the above-mentioned composition, the said fine cutstrands being such as that commercially known as shredded foil andproduced by the method and apparatus described and claimed in US.Patents 2,297,368 and 2,331,230, Rippl et 211., suchshredded foilstrands having a width ranging from approximately 0.5 to 1.5 mils and athickness likewise ranging from approximately 0.5 to 1.5 mils. In thecase of the preferred form of flash lamp according to the invention,employing a bulb 1 having a volume of approximately 1.2 cc., the bulb isfilled with around 24 milligrams of zirconium shredded foil theindividual strands of which have a thickness of about 0.0008 inch and awidth of about .0012 inch.

The envelope or bulb 1 also contains a filling of a suitablecombustion-supporting gas'such as oxygenor an oxygen-containing gas at asuitable pressure for supporting the combustion of the combustiblematerial. The oxygen or other combustion-supporting gas is introducedinto the bulb 1 through a glass exhaust tubulation at the top end 3 ofthe bulb which tubulation, after the evacuation of the bulb therethroughand the introduction of the oxygen or other combustion-supporting gasinto the bulb, is then tipped off as indicated at 4 to hermetically sealthe bulb. In the case of the preferred form of flash lamp according tothe invention, the bulb is filled with oxygen at a pressure of at leastapproximately 5 atmospheres and preferably ranging between 5 to 6atmospheres. The bulb 1 is coated on its outer surface with a protectivelacquer coating 8 such as cellulose acetate to thereby strengthen thebulb and to render it substantially shatterproof.

Sealed into the stem press end 2 of the bulb 1 is a lamp ignition mount9 comprising a pair of lead-in wires 10 which, in the manufacture of thelamp, are sealed into the stem press 2 so as to extend therethrough andinto the bulb 1 in a direction approximately longitudinally of the bulband in more or less side-by-side closely spaced relation. Outwardly ofthe stem press 2, the lead-in wires 10 are bent or looped back uponthemselves, with their free ends reentered and sealed in the glass ofthe stern press 2, to thereby form loop-shaped wire terminal contactmembers 11 which are respectively bent around the end of the stem pressto extend alongside the opposite flat sides S'thereof but terminatingshort of the guide channelways 6 therein. Interiorly of the bulb 1, thelead-in Wires 10 are rigidly tied together and held in place by asupport bead 12 of glass or other suitable insulating material in whichthe lead-in wires are embedded.

Mounted on and connected across the, inner ends ofthe lead-in wires 10,within effective ignition range of the combustible material 7 in thebulb, is a lamp ignition filament 13 preferably consisting of a shortstraight length of fine tungsten wire having a diameter preferably ofthe order of 0.7 mil. The inner ends of the lead-in wires 10,

and the portions of the ignition filament 13 at the points' ofconnection thereof to the lead-in wires 10, are coated with a layer offulminating substance or primer material 14 to form beads of suchmaterial which become ignited when the ignition filament 13 is energizedand heated. The fulminating or primer material 14 is applied to thelead-in wires 10 and filament 13 in the form of a paste consisting, ingeneral, of extremely sensitive metal powder and suitable powderedoxidizing material mixed with a suitable binder.

7 w is.

The fulminating or primer material 14 which has been found to be mostsatisfactory and has been most commonly employed for the effectiveignition of flash lamps of the type employing filamentary combustiblematerial consisting of either substantially pure aluminum or purezirconium, has been of the general composition disclosed in US. Patents2,280,598, Meredith, and 2,756,577, Anderson, and comprising a powderedmixture of zirconium, magnesium and potassium perchlorate powders bondedtogether by a suitable binder such as a solution of nitrocellulose inamyl acetate. For best results, and particularly where the ignitionfilament 13 is of a diameter of the order of 0.7 mil, it is preferredthat the relative proportions by weight of the above-named P wderingredients be within the particular ranges disclosed and claimed in theabove-mentioned Anderson Patent 2,756,577, such ranges being of theorder of, by weight, from 60-90% zirconium, 1-8% magnesium, and 9-35%potassium perchlorate.

In the case of extremely small size zirconium-filled flash lamps of thecharacter with which the invention is particularly concerned, it hasbeen found that when the material employed for the primer beads 14 is ofthe composition disclosed and claimed in either the aforesaid MeredithPatent 2,280,598 or in the Anderson Patent 2,756,577, the peak intensityof the light flash produced by the lamp occurs at a comparatively shortinterval of time, i.e., from 10 to 13 milliseconds, following theclosure of the electrical circuit to the ignition filament 13 of thelamp. As previously mentioned, while flash lamps with such a short timeto peak intensity may still be satisfactorily employed for so-calledclass F or fast type camera shutter synchronizer arrangements, they areunsuitable or use with the slower class M camera shutter synchronizerarrangements because of the insufiicient intensity of light from thelamp at the 20 millisecond time interval when the camera shutter reachesits fully open position with such class M synchronization, the intensityof the light by such time having fallen off to such a low level as to beineffective for picture-taking purposes.

In accordance with the invention, we have found that the incorporationin such primer compositions of definite amounts of one or more inert(i.e., non-combustible), and non-hygroscopic additive materials of lowoil-absorption character and having a high temperature decompositioncharacteristic will operate to retard or delay the peak time of thelight flash produced by such small size zirconium-filled lamps withoutcausing any attendant decrease either in the total amount or the peakintensity of the light produced by the lamp. In other words, by theaddition of such inert additive material to the primer composition, thetirne-ligh t intensity characteristic curve of such small sizezirconium-filled flash lamps is simply bodily shifted. or displacedfarther along the time scale from one exhibiting a comparatively shorttime to peak of around 10 to 13 milliseconds as shown by the curve A inFIG. 3 of prior small size zirconium-filled flash lamps, to one having alonger time to peak of at least 15 to 16 milliseconds or so as shown bythe curve B of a flash lamp constructed according to the invention. As aresult of such displacement of the time-light characteristic curve tothat shown by the curve B, suflicient light intensity is therefore stillpresent, at the 20 millisecond time interval following energization ofthe lamp ignition filament, :to render the lamp utilizable for so-calledclass M synchronization wherein the camera shutter is in its fullyopened position at such 20 millisecond time interval.

The inert additive material which, in accordance with the invention, isincorporated into the primer coating 14 should be one having a hightemperature decomposition characteristic so that it does not excessivelyrob, from the sensitive zirconium and magnesium powder particles of theprimer beads 14, the heat which is normally supplied thereto by theignition filament 13 when heated by the passage of electrical currenttherethrough. In addi- 6 tion, the additive material should be one whichdoes not hydrate, i.e., it should be of non-hygroscopic character, so asnot to pick up any moisture, during lamp fabrication, such as wouldcause loss of adherence of the powder particle ingredients of the primerbeads 14 and result in flaking or crumbling of the primer material offthe lead-in wires 10. It is of most importance, however, that theadditive material incorporated into the primer composition comprisingour invention should be one of low oil-absorption character so as torequire very little binder to hold it together. As a result, little ifany increase in the binder ingredient of the primer composition isrequired in order to insure the required interadherence of the primerparticles and prevent the primer beads 14- from crumbling. If asubstantially greater amount of binder were required to obtain thenecessary primer particle interadherence, the added binder would, ineffect, desensitize the primer coatings or beads 14, the binder in suchcase acting to coat the sensitive zirmonium and magnesium particles ofthe primer composition so as to insulate them to some degree from theheat supplied by the ignition filament, when energized, vand thus eitherentirely preventing them from being heated to their ignition temperatureor else undesirably delaying their being heated to such ignitiontemperature.

For the purposes of the invention, we have found that certain oxides andsalts of the alkaline earth metals such as magnesium oxide and bariumsulfate, as well as titanium dioxide, are entirely satisfactory asadditive materials for incorporation into the primer compositionaccording to the invention. The material preferably employed for suchpurpose, however, and which has been found to be particularly suitablefor the purposes of the invention because of its outstandingly lowoil-absorption characteristic and its ready availability and low cost,is calcium carbonate, otherwise known as marble flour.

The amount of the inert additive material which is normally required tobe present in the primer composition in order to achieve the objects ofthe invention is in the general range of from approximately 5 to 35% byweight of the total powder ingredients of the primer composition. Thus,the primer or fulminating material employed for the ignition beads 14 ofthe flash lamp according to the invention consists essentially of apowder admixture of Marble flour magnesium, zirconium and potassiumperchlorate in the approximate proportions by Weight of between l8% ofmagnesium, 60-90% of zirconium and 9-35 of potassium perchlorate andcontaining approximately 5-35% by weight of the inert additive material.Expressed in terms of percent-age by weight of the total powderadmixture, the primer material comprising our invention is of thefollowing composition:

Percent Magnesium powder 0.5-7.5 Zirconium powder 40-85 Potassiumperchlorate powder 5-33 Inert additive material 5-35 Within the abovegeneral range of compositions, and particularly where marble flour isemployed as the inert additive material, the following primercomposition by weight has been found to be particularly advantageous:

Percent Magnesium powder 5-7 Zirconium powder 43-57 Potassiumperchlorate powder 1926 Marble flour 10-33 A specific primer admixturecomposition which has been found to be especially suitable for thepurposes of the invention consists of the above ingredients in thefollowing approximate proportions by weight:

Percent Magnesium powder 6 Zirconium powder 51 Potassium perchloratepowder 23 20 The zirconium, magnesium and potassium perchlorate powdersemployed in the primer admixture are of extremely fine character,preferably of the order of 325 mesh or finer. The particles of the inertadditive material are likewise of such a fineness. The zirconium metalpowder preferably is that commercially known as No. 3 grade,manufactured and sold by the Foote Mineral Company of Philadelphia,Pennsylvania, the said No. 3 grade zirconium powder having a relativelyhigh ignition point as compared to other forms of zirconium powders. Themagnesium metal powder employed is preferably that manufactured'by theUnited States Magnesium Company of Pleasant Valley, New York, and knownas their 325 mesh magnesium powder. Chemically pure (CP) grade crystalpotassium perchlorate powder is employed as the oxidizing agent in theprimer composition.

The primer material is appliedto the lead-in wire tips in the form of apaste or suspension of the powder particles in a suitable binderconsisting of around 8% solids and 92% volatile solvents. The subsequentvolatilizetion of the solvents in the binder then leaves a hardenedresidue 14 composed almost entirely of the zirconium, magnesium,potassium perchlorate and inert additive powder ingredients of theprimer paste. The binder preferably employed is a low percentage (i.e.,around to 10%) solution of nitrocellulose in amyl acetate, such a binderpreferably consisting of around 8% solids. Enough binder is employed toimpart the desired consistency to, the primer paste to produce therequired size primer beads 14 on the inner lead-in wire tips for a givenmanufacturing application procedure. Using the abovementioned specificbinder consisting of an approximately 8% solution of nitrocellulose inamyl acetate, the amount of binder solution employed will generallyamount to around 18% by weight of the primer paste composition. Aspecific example of a primer paste according to the invention which hasbeen found to be particularly satisfactory is of the followingapproximate composition:

Magnesium powder grams 4 Zirconium powder do 33 Potassium perchloratepowder do Marble flour do 13 8% nitrocellulose solution in amyl acetatecc.. 18

The primer paste material may be prepared in the following manner: theformula quantities of magnesium powder and zirconium powder are firstthoroughly mixed with enough of the formula quantity of binder to form athin paste, the amount of binder required for such purpose being added alittle at a time to the zirconiummagnesium powder admixture and beingthoroughly mixed together therewith after each such addition. Theremaining portion of the formula quantity of binder is next added, alittle at a time, to the formula quantities of potassium perchloratepowder and inert additive material and thoroughly mixed therewith aftereach such addition. The mixture of potassium perchlorate, inert additivematerial and binder thus formed is then added to and thoroughlyintermixed with the zirconium-magnesium-binder mixture to form thefinished primer paste composition.

The use of the primer composition according to our invention, in smallsize zirconium-filled lamps of the type referred to hereinabove, notonly acts to retardthe peak time of the lamp so as to accur around 15 to16 milliseconds following closure of the electrical circuit to the lampignition filament, without causing any corresponding significant loss inthe total light or peak intensity of the lamp, but it also serves tomarkedly lessen the susceptibility of such lamps to accidental flash-outby electrostatic charges such as are normally encountered in themanufacture and use of the lamps. Thus, we have found that by the use ofa primer composition according to the invention in small sizezirconium-filled flash lamps, the number of lamp flash-outs resultingfrom electrostatic charges has been reduced by as much as 50% or more,depending upon the amount of the inert additive material present in theprimer composition.

A most important aspect ofour invention, moreover,

' is the fact that the above-mentioned advantages are obtained whilemaintaining the size of the primer beads or coatings 1.4 at so-calledworkable sizes below which it would become impractical, from amanufacturing stand point, to control the size of the primer beadswithin the 11'. .its necessary to achieve satisfactory uniformity in thelight performance and operating characteristics of the lamps.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A flash lamp comprising a sealed envelope having an oxidizingatmosphere therein, a quantity of filamentary combustible materialloosely arranged within said envelop and consisting essentially ofmaterial of the group consisting of zirconium and metallic materialshaving a low heat-energy ignition characteristic substantiallycorresponding to that of zirconium, and ignition means disposed in saidenvelope within effective ignition range of said combustible material,said ignition means comprising a fulminating substance consistingessentially of mag nesium, zirconium, potassium perchlorate and marbleflour in the approximate proportions by weight of between 0.5-7.5 ofmagnesium, 40 to of zirconium, 533% of potassium perchlorate and 5 to35% of marble flour, said admixture ingredients being bonded together bya suitable binder.

2. A flash lamp comprising a sealed envelope having an oxidizingatmosphere therein, a quantity of filamentary combustible materialloosely arranged within said en velope and consisting essentially ofmaterial of the group consisting of zirconium and metallic materialshaving a low heat-energy ignition characteristic substantiallycorresponding to that of zirconium, and ignition means disposed in saidenvelope within effective ignition range of said combustible material,said ignition means comprising afulrninating substance consistingessentially of a powder admixture of magnesium, zirconium, potassiumperchlorate and marble flour in the approximate proportions by weight ofbetween 5-7% of magnesium, 43-57% of zirconium, 1926% of potassiumperchlorate and 10-33% of marble flour, said admixture ingredients beingbonded together by a suitable binder.

3. A flash lamp comprising a sealed envelope having an oxidizingatmosphere therein, a quantity of filamentary combustible materialloosely arranged within said envelope and consisting essentially ofmaterial of the group consisting of zirconium and metallic materialshaving a low heat-energy ignition characteristic substantiallycorresponding to that of zirconium, and igintion means disposed in saidenvelope within effective ignition range of said combustiblematerial,said ignition means comprising a fulminating substance consistingessentially of a powder admixture of magnesium, zirconium, potassiumperchlorate and marble flour in proportions, by weight, of the order of6% magnesium, 51% zirconium, 23% potassium perchlorate and 20% marbleflour, said admixture ingredients being bonded together by a suitablebinder.

References Cited in the file of this patent UNITED STATES PATENTS2,098,341 Kalberg Nov. 9, 1937 2,375,742 Kalil et a1. May 8, 194-52,756,577 Anderson July 31, 1956 2,798,368 Anderson July 9, 19572,982,119 Anderson May 2, 1961 FOREIGN PATENTS 604,488 Great BritainJuly 5, 1948

1. A FLASH LAMP COMPRISING A SEALED ENVELOPE HAVING AN OXIDIZINGATMOSPHERE THEREIN, A QUANTITY OF FILAMENTARY COMBUSTIBLE MATERIALLOOSELY ARRANGED WITHIN SAID ENVELOP AND CONSISTING ESSENTIALLY OFMATERIAL OF THE GROUP CONSISTING OF ZICONIUM AND METALLIC MATERIALSHAVING A LOW HEAT-ENERGY IGNITION CHARACTERISTIC SUBSTANTIALLYCORRESPONDING TO THAT OF ZIRCONIUM, AND IGNITION MEANS DISPOSED IN SAIDENVELOPE WITHIN EFFECTIVE IGNITION RANGE OF SAID COMBUSTIBLE MATERIAL,SAID IGNITION MEANS COMPRISING A FULMINATING SUBSTANCE CONSISTINGESSENTIALLY OF MAGNESIUM, ZIRCONIUM, POTASSIUM PERCHLORATE AND MARBLEFLOUR IN THE APPROXIMATE PROPORTIONS BY WEIGHT OF BETWEEN 0.5-7.5% OFMAGNESIUM, 40 TO 85% OF ZIRCONIUM, 5-33% OF POTASSIUM PERCHLORATE AND 5TO 35% OF MARBLE FLOUR, SAID ADMIXTURE INGREDIENTS BEING BONDED TOGETHERBY A SUITABLE BINDER.